d = 02d20d2(2)(2Tpair)2.
 In the usual BCS case the phase fluctuations are costly and \(T_{\mathrm {c}}\approx T_{\mathrm {pair}}\) . In our case due to smallness of the Fermi energies, the condensation of pairs may happen at lower temperature, \(T_{\mathrm {c}}\le T_{\mathrm {pair}}\) . We estimate \(T_{\mathrm {c}}\approx \frac{\pi }{2}\rho _{\mathrm {s}}\)  where \(\rho _{\mathrm {s}}(T=0)\)  is the superfluid-stiffness following Ref. [1]}. Note that in two dimensions, the superconducting
transition temperature \(T_c \sim \rho _s(T_c)\)  (see, e.g., Refs.[2]}, [3]}).
The interplay between \(T_c\)  and \(T_{pair}\)  depends on the ratio
\(\rho _s (T = 0)/T_{pair}\) . If this ratio is large, the superfluid stiffness rapidly increases below T\(_{pair}\) . In this situation, \(T_c = T_{pair}\)  minus a small correction, i.e., the phases of bound pairs order almost
immediately after the pairs develop (phase fluctuations cost
too much energy). If \(\rho _s (T = 0)/T_{pair}\)  is small, \(\rho _s (T)\)  increases slowly below T\(_{pair}\)  and \(T_c\)  is of order \(\rho _s (T = 0)\) . In Ref.[1]} its expression was extended to the multiband case where \(\rho _{\mathrm {s}}\)  is given by \(\rho _{\mathrm {s}}\approx \rho _{\mathrm {e}}+\rho _{\mathrm {h}}\) ,

e=116202d0de2Ee(k)3
